Challenging Horizontal Well Placement in an Area with High Geological Uncertainty Using Proactive Geosteering Techniques

Abstract

AbstractNew technologies, including drilling horizontal wells, have evolved to enhance hydrocarbon production. Drilling profitable horizontal wells requires using available information to minimize uncertainty and proactive geosteering techniques to maximize production by navigating within the sweet spot.When available information is based on 2D seismic and well correlation, advanced geosteering techniques are used to anticipate resistivity changes along the well trajectory, which can be used before and during the drilling process to successfully place a horizontal well. The geosteering process is performed using azimuthal wave propagation resistivity and gamma ray. For landing, an adequate stratigraphic correlation has been crucial. However, for the lateral section, geosignals and azimuthal resistivity measured at different depths of investigation from the top and base of the borehole have helped determine the section with best reservoir characteristics. This paper presents the results obtained in four horizontal wells in which proactive geosteering techniques have helped to position and navigate the wells along the sweet spot.The Lower U Sandstone (Cenomanian) at the Sacha field has become the target for horizontal wells because of the reservoir characteristics present. Offset wells located in the flanks of the structure do not show the presence of water/oil contact in well logs; however, production data proves otherwise. Likewise, the deepest resistivity readings have shown a more conductive zone in the lower portion of the reservoir, which has never been crossed with a horizontal well. After a well is closer to the latter zone, azimuthal and average deep resistivities measure less resistivity than in the upper portion, whereas gamma ray values remain constant; these results are interpreted as clean sandstone. This information helped the team make the right decisions to minimize possible water breakthrough from this zone.The horizontal well drilling process, using advanced proactive geosteering techniques, has helped determine that the flanks of the structure present a less prospective zone and contain less hydrocarbon saturation. Finally, the experience gained by the team, using these techniques and tools could help improve performance in future horizontal wells.